1. Field of the Invention
The present invention relates to a method for jointing an optical fiber and an optical lens, an apparatus for the same and an optical module.
2. Description of the Related Art
As one of basic modules used in the optical communication, there is the fiber collimator. The fiber collimator is the module in which the optical fiber and the lens are integrated together, and used to execute the emittance and incidence of the beam in response to the lens characteristics.
Heretofore, in manufacturing such fiber collimator, the end portion of the optical fiber and the lens are jointed by using the adhesive. More particularly, the fiber is passed previously through the tubular guide called the capillary or the ferrule before jointing, then the fiber is fixed under the condition that end portions of the tubular guide and the fiber are aligned, then a tip of the fiber is polished to consist with an end face of the guide, and then the optical fiber together with the guide is jointed to the lens while matching the optical axis of the lens with the optical axis of the fiber.
Also, such a structure is proposed that the optical fiber and the lens are arranged to provide a space between the end face of the optical fiber and the end face of the lens and then jointed without the adhesive (see U.S. Pat. No. 5,889,904). In this case, an antireflection coating is coated on the end face of the lens to satisfy the optical characteristics, and then the optical fiber and the lens are fixed after their positional relationship is adjusted.
However, in the structure that the optical fiber and the lens are jointed by using the adhesive, such adhesive absorbs a part of the passing light. Therefore, when the high-intensity light is incident, in some cases the temperature rise is caused and thus the adhesive is altered in quality and also the optical characteristics are deteriorated.
Normally, the absorption of the optical adhesive is about 1 to 5% in the wavelength range used in the optical communication. The change in quality is caused in the adhesive that has tolerance for the high temperature when the temperature exceeds about 400 degree centigrade. However, the adhesive having such tolerable temperature range cannot withstand the light intensity of up to several [W] class.
Also, according to the jointing approach using the above adhesive, since the optical fiber is held onto the guide such as the capillary and then the polishing operation is required to register both end faces, there existed the problems that the work becomes troublesome and also a product cost is increased.
In addition, in the case where the two-core fiber (two single-core fibers and the two-core tape fiber) is jointed to the collimator lens, respective fibers are inserted into the holed guide (capillary, or the like) having two holes or one hole therein, then two fibers are secured by the adhesive or the like in the state that two fibers are kept close, and then the end faces of the fibers together with the guide are polished to align the end faces. This is because two fibers cannot be jointed with a small loss unless their end faces are aligned with good precision, and because reduction in size of the structure cannot be achieved if two fibers are parted from each other.
Also, as shown in U.S. Pat. No. 5,889,904, in the case of the method of jointing the optical fiber and the lens to provide the clearance space between them, such a disadvantage existed that it is possible that the optical characteristics are deteriorated because of a foreign matter entered between the end faces.
Also, since their end faces are not fixed mutually by the adhesive, or the like, another structure is needed to fix their positional relationship and still maintain such positional relationship after the jointing is completed. Therefore, such disadvantages existed that increase in the number of articles and the number of working process is brought about and also it is difficult to attain a lower cost and a smaller size.
Also, since the antireflection coating on respective end faces of the fiber and the lens is needed, such disadvantages existed that a higher cost is caused and also the optical characteristics are influenced by the light resistance of the antireflection coating.